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175 Cards in this Set
- Front
- Back
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Salivary Glands are what kind of glands?
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compound tubulo-acinar glands
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Parenchyma of Salivary Glands are composed of what kind of structures?
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terminal secretory end structures (acini & tubules) which drain via a series of ducts into the oral cavity
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Secretory Elements supported via
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connective tissue
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Terminal secretory end structures consist of
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groups of cells surrounding a central lumen
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2(could be 3) types of secretory cells in end pieces
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1 - Serous
2- Mucous 3rd type - sero-mucous cell |
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Location of myoepithelial cells
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btwn secretory cells & surrounding basal lamina
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Oncocytes
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found in aging glands
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Location of serous cells
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spherical end pieces or acini.
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Location of mucous cells
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tubular end pieces
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Mixed serous-mucus glands
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Mucus tubules open into proximal part of the duct system (intercalated ducts)
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Where are small groups of serous cells cells
(crescent shaped demilunes) located? how do their secretions reach the lumen? |
on the outer surface of the mucous tubules and their secretions reaches the lumen by passing along canaliculi between the mucous cells
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What shape are serous cells?
How are they arranged? In how many layers are they organize? |
pyramidal-shaped cells, arranged in acini.
organized in a single layer around the small central lumen of acinus |
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Narrow, apical ends of serous cells
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abut the acinar lumen
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Nucleus of serous cells
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vesicular, spherical nucleus located in the basal one-third of the cytoplasm
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Basal region of serous cells
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packed w/ rER & stains basophilic
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Cytoplasm of serous cells
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considerable amount of golgi material
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Apical region of serous cells
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contain secretory zymogen granules =eosinophilic
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Serous cells produce
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proteins & glycoproteins including enzymes (amylase), antimicrobial & calcium binding substances
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What separates the luminal surface from the basolaterial surfaces of the serous cell?
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Junctional complexes
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Tight junctions of serous cells
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help maintain surface domains & regulate passage of material between the lumen & intercellular space.
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Canaliculi
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fingerlike extensions of the lumen located btwn adjacent serous cells
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Lateral cell membranes of serous cells
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form the walls of the canaliculi
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Between adjacent serous cells, along the length of the canaliculi cells you may find many:
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desmosomes & gap junctions
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Microvilli of serous cell
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project from the lateral cell membranes into the lumen of the canaliculi.
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Basal surface of serous cells
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has regular folds that extend laterally beyond the borders of the cell to interdigitate with folds of adjacent cells.
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Mucous Cells
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arranged in elongated secretory end structures = mucous tubules
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Mucous cells lack
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intercellular canaliculi except for those covered by serous demilune cells
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Central lumen of mucous tubules
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wider than serous acini
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Distinguishing mucous cells from serous cells
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Mucous cell nuceli are compressed against their basal cell membrane by the secretory granules or droplets, which occupy most of the cytoplasm.
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Mucigen granules
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contain mucous glycoproteins.
Classified as glycoproteins even though they are mainly carbohydrate |
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Mucins (hydrophilic/hydrophobic)
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hydrophilic glycoproteins
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When mucins are released from the cell
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b/c highly hydrated & form mucous
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Cytoplasm of mucous cells
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appears foamy in routinely stained tissue b/c mucigen stains very weakly w/ H & E
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H & E stain of mucous cytoplasm
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leaves only a few strands of positively stained cytoplasm btwn empty spaces (mucigen droplets)
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Staining of mucigen droplets
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mucicarmine or PAS (periodic acid - Schiff reagent) b/c of their carbohydrate content
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Golgi complex of mucous cells
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large
located mainly basal to secretory granules |
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rER & organelles of mucous cells
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limited to the basal cytoplasm
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Myoepithelial cells
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non-secretory cells found btwn the basal cell membrane of secretory cells & basement membrane which surrounds tubules & acini
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How many myoepithelial cells are associated with each secretory end structure
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3
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Are myoepithelial cells found on the outer surface of intercalated ducts?
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yes
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Cell body of myoepithelial cells
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nucleus & several long processes which wrap around secretory or duct cells ->octopus shaped
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Role of myoepithelial cells
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may play a contractile role during glandular secretion
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How are myoepithelial cells joined to adjacent epithelial cells?
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desmosomes
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What characteristics of smooth muscle do myoepithelial cells have?
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contain myofilaments,dense bodies & attachment plaques
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Oncocytes
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appear in increasing numbers in aging salivary glands where they replace serous secretory cells & duct lining cells.
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Oncocytes (histology)
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cuboidal - low columnar & have an eosinophilic, granular cytoplasm due to the presence of a lot of mitochondria.
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Functional significance of oncocytes
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unknown
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Saliva formation
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occurs in 2 stages
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Primary Stage of Saliva formation
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produced by cells in the secretory end pieces & intercalated ducts.
isotonic fluid containing most of the organic components & all the water secreted by salivary glands |
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How does water enter saliva?
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only via secretory end structures & intercalated ducts.
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Water movement in striated & excretory duct regions
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little water movement
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Second stage of Saliva formation
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Primary saliva is modified as it passes through striated & excretory ducts mainly via resorption & secretion of electrolytes.
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Saliva entering the oral cavity is
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hypotonic
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Secretory protein synthesis
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occurs by rER & packaged into secretory granules by Golgi complexes.
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Norephinephrine's role in secretory protein synthesis
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NE=sympathetic nt, binds to B adrenergic receptors on the surface. Begins sequence of G protein.
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What sequence leads to granule exocytosis?
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G-protein, adenyl cyclase, cAMP, protein kinase , and a cascade of phosphorylation of other proteins.
Granules fuse w/ apical membrane & release their contents. |
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How is the secretion of water by cells of secretory end pieces regulated?
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via parasympathetic nerves.
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How do parasympathetic nerves regulate the secretion of water by the secretory end pieces?
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Binding of ACh to surface cholinergic receptors & NE to alpha adrenergice receptors activates a Ca - phospholipid pathway resulting in release of CA from intracellular stores
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What release pathway is followed by parasympathetic regulation?
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ACh - G protein - PLC - PIP2 - IP3 - Ca
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What does increased Ca concentration do?
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opens Cl - channels in the apical membrane
opens K + channels in the basolateral membrane & activates the basolateral Na+/K+/2Cl - cotransporter. |
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What does the efflux of Cl- through the apical membrane into the lumen do?
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pulls extracellular Na into the lumen via tight junctions.
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An osmotic gradient is created by
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increased Na and Cl luminal concentrations
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Osmotic gradient results in
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movement of water into the lumen via the transcellular route & aquaporins in the apical membrane & via paracellular route across tight junctions
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How is the intracellular ionic & osmotic balance maintained?
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via Na, Cl, K entering the cell through the basolateral membrane via Na, K, 2Cl cotransporters & Na/K pumps.
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Fluid secretion is driven by
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active transport of electrolytes.
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Cells also secrete via other mechanisms
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Apical Cl channel is believed to transport HCO3 into the lumen
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At high flow rates, salivary HCO3 concentrations
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increase
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A basolateral _______________ serves to restore intracellular pH following acidification that occurs as a result of HCO3 secretion
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Na/H coupled antiport carrier protein
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What happens to the pH of saliva as flow rate increases?
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pH of saliva increases as flow rate increases b/c HCO3 concentration increases at higher flow rate
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What system modifes the primary saliva produced by the secretory end pieces?
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duct system
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Salivary glands & Ducts
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possess an extensive system of branching ducts.
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Secretory end structures empty into
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small intercalated ducts
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small intercalated ducts drain into
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somewhat larger, but still intralobular, striated ducts
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Excretory Ducts
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interlobular
receive saliva from striated ducts & open onto the mucosal surface |
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Intercalated Ducts
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narrowest part of the duct system
receive saliva directly from secretory units empty into striated ducts |
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simple low cuboidal epithelium which contain a small amount of rER lines
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intercalated ducts
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Difficulty in seeing intercalated ducts b/c
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they are compressed btwn secretory units
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What do intercalated ducts contribute to saliva?
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macromolecules including antibacterial substances, lysozyme & lactoferrin.
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Striated Ducts
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located w/i lobules & easily identified b/c they are the largest intralobular structures.
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Lining of striated ducts
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lined by simple columnar epithelium
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Nucleus of striated ducts
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central ovoid nucleus
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Cytoplasm of striated ducts
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eosinophlic cytoplasm
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Pink necklaces
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striated ducts are readily apparent against the background of basophilic serous acini in the parotid.
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What creates the appearance of basal striations which characterize striated ducts?
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basal plasmalemma of the lining cells is deeply folded and there are parrallel rows of elongated mitochondria between folds
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Striated ducts are longer in
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submandibular glands
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Apical cytoplasm of striated ducts
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contains small secretory granules & electron lucent vesicles.
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Secretory granules of striated ducts contain secretory proteins including:
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kallikreins.
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Kallikreins
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cleave kiniogens during blood clotting
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Electron - Lucent vesicles
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may play a role in endocytosis of substances from the lumen.
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Striated ducts drain into
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excertory ducts
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excretory ducts
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located btwn lobules of glandular parenchyma and therefore interlobular
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What surrounds excretory ducts?
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collagenous connective tissue
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Cells lining the excretory ducts
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gradually lose the features which characterize striated ducts and the lining epithelium b/c pseduostratified or stratified columnar.
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Lining of excretory ducts
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contain columnar cells, smaller basal cells, and some goblet cells.
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Do excretory cells have small numbers of brush(nerve receptor) cells & dendritic antigen presenting cells?
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yes
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What does the lining of the excretory duct b/c as it approaches the oral mucosa?
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stratified squamous epithelium
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What does the excretory ductal epithelium ultimately merge with?
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w/ stratified squamous epithelium which covers the oral mucosa
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Primary saliva secretion is produced by
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secretory end structures & intercalated ducts is isotonic w/ serum.
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Saliva remains isotonic as it passes along
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intercalated ducts which may secrete antibacterial substances
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Intercalated ducts may secrete
antibacterial substances such as |
lysozyme & lactoferrin into the saliva.
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As saliva passes through the striated & excretory ducts
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saliva b/c hypotonic
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What does the striated duct cell pump?
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pumps Na from saliva across its cystoplasm and into adjacent capillaries.
Cl ions accompany Na. K and HCO3 are secreted |
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Saliva enters the striated duct isotonic but leaves hypotonic b/c
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more Na and Cl are reasorbed than K and HCO3 are secreted
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Final electrolyte composition of saliva is affected by its
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flow rate among the ducts
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Greater secretory flow rate along the ducts
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the higher the tonicity of saliva
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At max flow rates, the tonicity of saliva is
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70% of that of plasma
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At high flow rates, saliva is in contact w/ ductal epithelium for a
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short time, so Na and Cl concentrations are relatively higher and K concentration is lower.
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HCO3 concentration increases during
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high flow rates, reflecting increased HCO3 secretion by acinar cells to drive fluid secretion
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Electrolyte reabsorption & secretion by striated & exceretory ducts is regulated by
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ANS and aldosterone
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Aldosterone
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causes Na reabsorption from saliva, sweat & urinary filtrate.
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Major salivary glands are surrounded by
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collagenous ct capsule which extends to the parenchyma as septae or trabecula which divide the gland into lubules.
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Minor glands
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lack a distinct capsule
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Areolar connective tissue supports
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acini and tubules
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Plasma cells in salivary gland ct produce
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dimeric IgA
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Dimergic IgA is released into the
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strome
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IgA dimer is linked by a
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J chain
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Salivary gland epithelial cells have a surface receptor (secretory component) for
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IgA
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What happens to IgA molecules linked to the secretory component?
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they are pinocytosed by the epithelial cells and the immunoglobin and secretory component are released as part of the salivary secretion.
= secretory IgA |
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What does the IgA dimer bind to?
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a poly- Ig basolateral surface of epithelial cell
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Poly Ig receptor
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has an attached extracellular secretory component- SC
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Where does the IgA-poly-Ig receptor-SC complex go?
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its internalized and moves across the cell to its apex via transcytosis.
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Cleavage of the IgA-poly-Ig receptor-SC complex releases
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IgA-SC
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Adipocytes in aging salivary glands
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increase - particularly in the parotid
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Parotid gland secretion
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purely serous secretory acini in adults.
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Intercalated ducts of Parotid gland
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very long intercalated ducts
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Striated ducts of Parotid gland
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short
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Main excretory duct for Parotid gland
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Stensen's gland
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Submandibular gland secretion
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contains mucous tubues, but consists mainly of serous acini.
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Intercalated duct of submandibular gland
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shorter than those of Parotid gland
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Striated ducts of submandibular gland
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longer than Parotid gland
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Main excretory duct of submandibular gland
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Wharton's Duct
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Major sublingual gland secretion
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predominantly mucus although it has some serous acini.
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Ducts of major sublingual gland secretion
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none are prominent
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Main excretory duct of the major sublingual gland
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bartholins's excretory duct
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Main excretory duct of the major sublingual gland may join
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Wharton's duct or it may open on the surface of the sublingual fold.
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Minor Salivary gland secretion
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mainly mucous w/ single exception
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Von Ebner
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minor salivary gland which is a serous gland (its an exception)
associated w/ circumvallate & folliate papillae |
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Location of minor glands
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located throughout the oral mucosa, except for the gingivae, anterior hard palate & anterior 2/3 of the dorsal surface of the tongue
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Minor glands produce what percentage of total saliva?
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Approx 7 - 10 %
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Daily salivary production
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600 - 1,000 mLs.
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Whole Saliva flow rate/Stimulated flow rate
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2.0 - 5.0 mLs/min during eating
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Resting/non stimulated flow rate during waking hrs
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.2-.4 /min
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Amount of saliva secreted at night
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0 - 10 mLs
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Stimulated flow rate for parotid gland
stimulated flow rate for combined submandibular and sublingual glands |
.5 - 2.0 mLs/min
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Major glands contribute more than what percentage of saliva?
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90%
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What does the viscosity of saliva depend on?
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depends on the ratio of concentrations made to it by the various glands.
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Parotid glands secrete
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clear, watery saliva rich in enzymes such as amylase, proline rich proteins, and glycoproteins
many of these proteins adhere to surface of teeth and mucosa or are degraded and presented in lower amounts in whole saliva |
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Secretions from glands other than the parotid gland are
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more cloudy & viscid
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Submandibular gland secretory components are similar to
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those of the parotid but also contain mucous
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Sublingual glands produce viscous saliva rich in
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mucigens
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minor salivary gland secretion represents less than --- % of whole saliva
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10%
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Minor salivary gland secretion accounts for ---% of secreted mucous
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70%, therefore its much more viscid than that of the major glands.
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Main component of saliva (90%)
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water
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Important constituents of saliva
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amylase, lysozyme, secretory IgA, glycoproteins (mucins), and electrolytes (Na,K,Cl,HCO3,Ca & HPO4.
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Oral fluid (mixed/whole saliva) contains
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desquamated epithelial cells, microorganisms,food debris, serum components, and inflammatory cells reaching the oral cavity via gingival crevice.
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2 Functions of Saliva
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keeping mucosa moist
protecting tooth surface from caries by constant deposition of salivary mucoprotein and sialoprotein onto tooth surface. |
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Lubrication
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swallowing and speaking are enhanced by the presence of mucous glycoproteins
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Mechanical washing
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washing of the oral cavity is enhanced by the presence of a large volume of water.
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Tooth surface protection by
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enamel pellicle
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Enamel pellicle
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formed by salivary glycoproteins.
Enamel pellicle binds to the tooth surface, and is Ca binding. It creates a local supersaturated solution of Ca & phosphate ions. |
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What does the enamel pellicle do to enamel dissolution?
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reduces
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What does the enamel pellicle do to remineralization of early enamel lesions
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enhances
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Antimicrobial activity is present in saliva:
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mucous barrier,lysozymes, thiocynate ions,lactoferrin,serum immunoglobins,IgA
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Mucous barrier in saliva
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-antimicrobial activity
prevents microorganisms adhering to the oral mucosa |
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lysozyme in saliva
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-antimicrobial activity
hydrolyzes polysaccharides in the cell wall of some bacteria |
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Thiocynate ions
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-antimicrobial activity
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Lactoferrin
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-antimicrobial activity
enhance immunoglobulin activity |
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Serum immunoglobulins
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-antimicrobial activity
enter the oral cavity in gingival fluid |
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IgA
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-antimicrobial activity
dominant antibody in fluids coating cavities which communicate with the exterior. inhibits adherence of microorganisms to oral tissues. |
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What renders IgA to be relatively resistant to destruction?
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its secretory component
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Buffering
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Saliva (bicarbonate & phosphate ions) neutralizes acids in foods & acids produced by bacteria from sugars
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Buffering prevents the growth of
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bacteria, which need a special pH.
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Digestion: amylase
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breaks down complex carbs to glucose & maltose
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Digestion:lipase
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breaks down triglycerides to diglycerides, monoglycerides & fatty acids
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Digestion:Saliva
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helps taste activity by dissolving food stuffs which are then detected by taste buds
neutralized gastric juice enhances bolus formation |
